Method of forming unsaturated acid esters



Patented Feb. 7, 1950 METHOD OF FORMING UNSATURATED ACID ESTEBS Hugh J.

signor Hagemeyer, Jr., Kingsport, Tenn., asto Eastman Kodak Company, Rochester,

N. Y., a corporation of New Jersey No Drawing. Original application June 7, 1946,

Serial No. 675,304. Divided and this application September 10, 1947, SerialNo. 773,295

- 2 Claims.

This invention relates to the condensation of a ketene with an ester of a keto acid and more particularly to a process for the preparation of ester lactones by this condensation. The invention also relates to the preparation of unsaturated acids bythe decarboxylation of these lactones and to the hydrolysis and alcoholysis of these lactones.

An object of the invention is to provide new ester lactones and a process for their prepara tion. 5

Another object is to prepare unsaturated dicarboxylic acids from my novel ester lactones.

Still another object of the invention is to prepare organic compounds by the hydrolysis or alcoholysis of ester lactones.

In accordance with one feature of the invention, these and other objects are attained by condensing a ketene with an ester of a keto acid in the presence of a Friedel-Crafts type catalyst to form an ester lactone.

Because of the great reactivity of ketenes and their tendency to polymerize and because of l the relative instability of the resulting beta lactones, it is preferable to carry out the reaction under mild conditions using a relatively low catalyst concentration and low temperatures. To

control the rate of reaction, organic diluents may be employed in the reaction mixture. Temperatures below 50 C. are usually desirable, and with the more active type catalysts temperatures as low as 70 C. may be employed.

, The invention is further illustrated in the following equation showing the condensation of a ketene with an ester of a keto acid to give an ester lactone of a carboxylic acid ester.

Wherein n represents any whole number, e. g. 1, 2, 3, 4, etc., R1 and R2 each represents hydrogen or hydrocarbon, and R3 and R4 each represents a hydrogen atom, an alkyl group, e. g. methyl, ethyl, etc., an aryl group, e. g. ph'enyl, benzyl, etc. and an aralkylgroup, e. g. phenylethyl, etc.

The simple ketene, CHF C O, formed by the pyrolysis of acetic acid or acetone is preferably employed as the 'ketene in the reaction, but its aliphatic and aromatic homologs including both aldol and keto ketenes may be employed. Desirable esters 'o'f keto acids for the reaction include the esters of pyruvic, aceto-acetic and levulinic acids. Various Friedel-Crafts type catalysts may be employed, such as halides of boron,

zinc, aluminum, tin, titanium, and iron or complexes of these halides with organic compounds such as ethyl ether, ethyl chloride and the like. These catalysts are well known in Friedel Cr'afts reactions.

The invention will be more clearly understood from the following examples:

Example -1 4 cc. of BF: 'ethe'rate catalyst are dissolved in 500 grams of ethyl ac'etoacetalte "at 0 C. contained in a reactor adapted for temperature control. Ketene is passed in through a high speed stirrer at a rate of 21 grams/hr. for 16 hours. 412 grams of the lactone of y-carbethoxy- B-hydroxy-e-methyl butyric acid were obtained. The reaction is shown in the following equation:

0 CH2=C=O 01130 ocmc/ 0 CH: CQHEO&-CEZ(IJOHZC=O Example 2 20 grams of methyl pyruv'ate in 30 cc. of isopropyl ether containing 1 cc. of boron trifluoride etherate were treated with one more of ketene at C. for 4 hours. 14 grams of the lactone of fi-carbornethoxyefi-hydroxy butyric acid was obtained. The reaction is shown in the following equation:

I have found that as the separation of the carbonyl group from the negative effect of the carboxyl group increases, the rate of the reaction increasesand a higher conversion is obtained.

In accordance with another feature of the invention, unsaturated acid esters can be prepared by the decarboxylation of the ester lactones of carboxylic acid esters of the type made as just described. The general equation may be shown as follows:

in which R1, R2, R3, R4 and n have the significance heretofore described.

The decarboxylation of the ester lactones to produce unsaturated acid esters is further illustrated in the following example:

Example 4 20 grams of methyl pyruvate in 30 cc. of isopropyl ether containing 1 cc. of boron trifluoride etherate catalyst were treated with one mole of ketene at 70 C. The reaction mixture was allowed to warm up slowly to 10 C. The catalyst was neutralized with sodium acetate and filtered out of the solution. The ester lactone thus formed was then decarboxylated by distilling at 100l20 C. at atmospheric pressure, and 8 grams of methyl methacrylate were obtained. The decarboxylation may be shown as follows:

in which R1, R2, R3, R4 and n have the significance heretofore described.

Example 5 43 grams of the lactone of 'y-carbomethoxy-phydroxy-B-methyl butyric acid, produced as described in Example 2, were hydrolyzed by adding 100 grams of 20% sodium hydroxide followed by acidification of the reaction mixture with hydrochloric acid to give oc-mGthYI-a-IIYCIIOXY succinic acid. The reaction may be shown as follows:

In accordance with still another feature of the invention, the ester lactones may be reacted with an aliphatic alcohol to give the corresponding mono ester of the dicarboxylic acid. The general equation may be shown as follows:

in which R1, R2, R3, R4 and n have the significance described above and R5 is an alkyl group, e. g. methyl, ethyl, etc.

Example 6 43 grams of the lactone of w-carbomethoxy-phydroxy-B-methyl butyric acid, produced as described in Example 2, were reacted with methyl alcohol to produce oc-IIlGthOXY a-methyl succinic acid ester. The reaction may be shown in the following equation:

These ester lactones produced by condensing a ketene with an ester of a keto acid can also be reacted with ammonia and amines and with halogen acids to produce valuable compounds.

This is a division of my copending application Serial No. 675,304, filed June 7, 1946, now Patent No. 2,456,503, dated December 14, 1948.

I claim:

1. The method of forming unsaturated acid esters having the general structure:

which comprises distilling under reflux a lactone having the general formula:

in which formulae R1 and R2 each represents a hydrogen atom; R3 and R4 each represents a member selected from the class consisting of a hydrogen atom; a methyl group, an ethyl group, a phenyl group, a benzyl group and a phenylethyl group, and n is a small whole number.

2. The method of forming methyl methaorylate which comprises distilling under reflux to decompose the lactone, having the formula:

HUGH J. HAGEMEYER, JR. No references cited. 

1. THE METHOD OF FORMING UNSATURATED ACID ESTERS HAVING THE GENERAL STRUCTURE: 